The fiber-reinforced plastics components can be produced with the aid of semifinished textiles products known as prepregs. Reactive prepregs are produced by preimpregnating a textile fiber material with a reactive, i.e. as yet unpolymerized, thermoplastic matrix material at a temperature lower than a polymerization-initiation temperature. The fiber-reinforced plastics component is shaped by mutually superposing the prepregs in a stack to give a layer package in a lay-up procedure and subjecting them to a thermoforming process or press process.
WO 2012/116947 A1 discloses a process of this generic type for the production of reactive prepregs, i.e. of continuous-fiber-reinforced semifinished sheet products with polyamide matrix. The process begins by preimpregnating textile structures with a liquid starting component of the polyamide matrix, i.e. molten lactam inclusive of added catalysts and/or activators, and specifically in a continuous process. After impregnation, the preimpregnated continuous textile structure is trimmed to size in a cutting unit to give fiber-reinforced semifinished sheet products and mutually superposed in a stacking unit to give a stack. In the further course of the process, the preimpregnated semifinished textile products are transported to an assembly unit in which the semifinished textile products are mutually superimposed in a lay-up procedure and are cut to size in accordance with the final shape of the required component. The resultant layer package is then placed in a mold. Shaping then takes place, and specifically at a temperature above the polymerization-initiation temperature in a press procedure or thermoforming procedure. The preimpregnated lactam thus polymerizes to give a polyamide. The simultaneous thermoforming/pressing converts the fiber-reinforced semifinished sheet product into the intended shape of the required component finishing.
Final trimming of the finished plastics component can then take place in a finishing unit, specifically with formation of final-trimming residues, composed of a composite of fibers and of the polymerized matrix material. The final-trimming residues can be delivered to a recycling unit, and can be further processed there to give a recyclate for uses in an injection-molding or press process, as indicated by way of example in EP 2 666 805 B1. Accordingly, it is possible, by simple comminution and extrusion, to introduce components based on a thermoplastic matrix into new uses in the injection-molding sector, for example. The fundamental advantage of fiber-composite materials based on a thermoplastic matrix here consists in excellent recycling properties. Simple melting and regranulation results in homogeneous mixing of the fibers and the matrix. The resultant recycled granulate can be reused as a high-quality feedstock for a very wide variety of applications.
The problematic part of the process sequence outlined above is that residues—additional to the final-trimming residue mentioned—are also produced at earlier junctures in the process: edge-trimming residues (from the trimming-to-size of the semifinished fiber products) and assembly-trimming residues. Unlike the final-trimming residue, the edge-trimming residues and the assembly-trimming residues have not yet been polymerized, and cannot therefore be further processed in the abovementioned recycling process. The edge-trimming residues and assembly-trimming residues are therefore diverted from the process sequence as non-recyclable waste material.